1. Field of the Invention
The present invention relates to silver halide color photographic light-sensitive materials and particularly to silver halide color photographic light-sensitive materials which form stabilized color images.
In greater detail, the present invention relates to a silver halide color photographic light-sensitive material which comprises a support and at least one silver halide emulsion layer on said support wherein at least one of said emulsion layers contains a hydrophobic phenol or naphthol type cyan dye forming coupler and at least one specific alkyl phosphoric acid ester as a coupler solvent and the stability to moisture or heat of the cyan dye images formed upon development is improved.
2. Description of the Prior Art
It has been known that when silver halide photographic light-sensitive materials are subjected to color development after exposure to light, the oxidized aromatic primary amine developing agent reacts with the dye forming couplers to yield indoaniline, indophenol, indamine, phenoxazine, azomethine or analogous dyes, by which color images are formed. In this process, a substractive process is generally used for color reproduction where yellow, magenta and cyan color images which are complementary colors to blue, green and red are formed. Generally, acyl acetamide type couplers are used to form yellow images, pyrazolone type couplers are used to form magenta images and phenol type or naphthol type couplers are used to form cyan images.
Conventionally, a hydrophobic photographic additive {for example, an oil-soluble coupler, an antioxidant for preventing color stain or color contamination, a color fade preventing agent (e.g., an alkylhydroquinone, an alkylphenol, a chroman, a cumarone, etc.), an oil-soluble filter dye, an oil-soluble ultraviolet absorbing agent, a compound capable of releasing a development inhibitor upon reaction with a developing agent (i.e., a DIR compound, such as DIR hydroquinone, a non-color forming DIR compound, etc.), a developing agent, a dye developing agent, a compound capable of releasing a diffusible dye by self-cleavage upon oxidation under alkaline conditions (i.e., a DRR compound), a compound capable of releasing a diffusible dye upon coupling with a color developing agent (i.e., a DDR coupler), and the like} is dissolved in an appropriate organic solvent having a high boiling point, dispersed in an aqueous solution of a hydrophilic organic colloid, in particular gelatin, in the presence of a surface active agent, and the resulting mixture is incorporated in a hydrophilic organic colloid layer, for example, a light-sensitive emulsion layer, a filter layer, a backing layer, an antihalation layer, an intermediate layer, a protective layer, and the like.
In such cases, a phthalic acid ester compound and an aryl phosphoric acid ester compound are particularly useful as the high boiling point organic solvent. These solvents are used in producing most color and black-and-white light-sensitive photographic materials as solvents for photographic additives (such as an oil-soluble incorporated type coupler, etc.). These solvents are described, for example, in U.S. Pat. Nos. 2,332,027, 2,533,514, 3,287,134, 3,748,141 and 3,779,765, German Pat. No. 1,152,610, British Pat. No. 1,272,561, German patent application (OLS) No. 2,629,842, etc. The high boiling point organic solvents of the phthalic acid ester and the phosphoric acid ester type are widely used due to their ability to disperse couplers, their affinity for a gelatin colloid layer, their influence on the stability of the color image formed, their influence on the hue of the color image formed, their chemical stability in photographic light-sensitive materials, their low price, and the like.
However, these high boiling point organic solvents do not always fulfill all the requirements such as dispersion capability for substantially water-insoluble photographic additives, affinity for an organic hydrophilic colloid layer, influence on the photographic properties, chemical stability in the photographic light-sensitive materials, and the like.
For example, some organic solvents having a high boiling point have a bad influence upon photographic properties (for example, they may cause light fading or fading in the dark of the color images obtained upon development), though they have good dispersibility, sometimes some solvents have properties opposite to the above described properties.
There are cases that color photographs are stored or displayed under exposure to light depending upon their intended use (for example, sometines they are displayed by exposure to very intense light, such as in the case of exhibition of G-color print films, exhibition of color printing paper or exhibition of color slides, etc. and there are cases when they are stored under comparatively mild conditions) and cases when they are stored in the dark for a long period of time while the period of time in which they are exposed to light is short (for example, color positive films for movies, color printing paper stored in albums, color slides and color negative films, etc.). Fading under the latter storage conditions is caused by moisture in the atmosphere or chemical substances present in very small amounts and by heat. This fading is called fading in the dark or thermal fading, which is distinguished from light fading which occurs under the former conditions. It is well known that dark-thermal fading of cyan images is a particularly more serious problem than that of yellow images or magenta images. This remarkable dark-thermal fading of cyan images becomes a large obstacle to using the color photographs as recording materials for semipermanent preservation. Even if the degree of fading of cyan images is low, the fastness of the cyan images is not balanced with that of the yellow images and that of the magenta images. Consequently, since the color balance deteriorates, it is necessary to increase the fastness of cyan images to that of other color images.
As means for preventing the dark-thermal fading of cyan images, various processes have been known. For example, there are processes which comprise processing color photographs with a stabilizing bath containing hydantoin compounds described in U.S. Pat. No. 2,579,436, carbohydrazides described in U.S. Pat. No. 3,201,244, tetramethylol cyclic alcohols described in U.S. Pat. No. 2,983,607, sugars and aminoacid derivatives described in U.S. Pat. Nos. 3,095,302 and 3,291,606, cysteine described in U.S. Pat. No. 3,201,243, polymethylol compounds described in U.S. Pat. No. 3,473,929, organic ferro-printing preventing agents (mercaptans and tautomers thereof, selenoalcohols and imino group containing heterocyclic compounds) described in Japanese Patent Publication No. 18257/73 or compounds described in U.S. Pat. Nos. 3,676,136 and 3,666,468 and 3,336,135. In these processes, however, not only is the improvement in the fastness of the cyan images insufficient, but also the compounds must be added in a large amount corresponding to about 0.5 to 20% by weight of the processing bath. Therefore, in the color photographs obtained by these processings, the surface of the films becomes sticky and causes undesirable problems, for example, adhesion when applied on an album. Further, through a process which comprises adding compounds described in Japanese Patent Publication No. 32728/73 to an emulsion layer has been proposed, the same effect as that in the processes using the stabilizing bath is obtained.
Since it is generally believed that couplers remaining in an unreacted state in the developed color photographs accelerate the fading of color images, processes which comprise removing the residual couplers have been proposed. For example, there is a process which comprises removing unreacted couplers from layers by diffusion, by splitting the couplers into low molecular fragments during the development processing (British Pat. Nos. 843,940 and 849,065) or a process which comprises dispersing water soluble couplers having a water solubilizing group on the coupling position thereof in emulsion layers in order to protect the dyes formed by development from the influence of the couplers and adding further a dispersion of a hydrophobic solvent which does not have a solvent function to the couplers but has a high solvent function to the dyes formed to the emulsion layers (U.S. Pat. No. 3,271,152).
However, in the former process, an additional processing bath for splitting the couplers into low molecular fragments is required and, in the latter process, there is complexity in the production step that the couplers and the hydrophobic solvent should be dispersed in the emulsion layers respectively. Accordingly, it is difficult to say that both of them are practical processes.
Further, as described in U.S. Pat. No. 3,614,839 and British Pat. Nos. 1,167,519 and 1,151,771, there are processes for improving the fastness of color images which comprise laminating color photographs with a transparent polymer film such as a polystyrene or polyethylene film after development. However, in these processes, not only much labor is involved in laminating but also a small effect is obtained for improving dark-thermal fading of cyan images.
On the other hand, as processes for improving dark-thermal fading of cyan images, processes described in Japanese patent applications (OPI) Nos. 161236/75, 26036/76 and 26037/76 have been proposed, where the coupler solvents are investigated. In these processes, however, not only is a sufficient effect not obtained for improving fastness of cyan images but also the coupler solvents do not always have satisfactory properties in their ability to disperse the oil-soluble couplers or their affinity for the hydrophilic colloid.
Incorporation of alkyl phosphoric acid esters in color photographic light-sensitive materials has been proposed in, for example, U.S. Pat. No. 3,676,137. However, the proposed invention is clearly different from the present invention, because alkyl phosphoric acid esters are used as coupler solvents for 5-pyrazolone type magenta couplers. Further, as described above, since the fastness to light, heat and moisture of magenta images is quite different from that of cyan images, different approaches are required respectively for preventing fading.
Further, in U.S. Pat. No. 4,009,038, a process which comprises dispersing phenol type or naphthol type cyan couplers and 2-(2'-hydroxyphenyl)benzotriazole compounds using dioctylbutyl phosphate has been proposed. This process, however, is very difficult to apply to photosensitive materials, because the emulsified dispersions have very low stability. Further, the invention in this patent application is clearly different from the present invention, because only dioctylbutyl phosphate is described and no experiment is described in said patent application.
Moreover, in U.S. Pat. No. T 969,005, a process which comprises dispersing a yellow coupler, a magenta coupler or a cyan coupler using trinonylphosphate or tridecylphosphate is disclosed. However, it has not been described in this patent application what effect can be obtained when the cyan coupler is dispersed using compounds having a branched carbon chain in the nonyl group or the decyl group.